1. Field of the Invention
This invention relates to a heat conduction pipe having a corrosion resistance used in fluid cooling pipes of automobiles and construction machines, air conditioners for regulating temperature and humidity of residential space, or the like under corrosive environment, and further is to obtain a heat conduction pipe that can exchange effectively heat according to great heat radiation property and endothermic property thereof as well as superiority in a corrosion resistance.
2. Description of Related Art
Conventionally, as a heat conduction pipe having corrosion resistance, some metal pipes such as described in Japanese Patent Application Publication Nos. JA-8-188884 and JA-10-315295 has existed, e.g., steel pipes or aluminum pipes hold anticorrosion plating, e.g., zinc plating or a chromate film; thermoplastic resin coating layer, e.g., polyamide (PA), polyptopylene (PP), polyethylene (PE), or the like is formed by means of extrusion molding on an outer circumferential surface of the metal pipe. By utilizing shock absorption, water resistance, chemical resistance, or the like of the resin coating layer, the anticorrosion plating layer and the metal pipe are prevented from receiving damages due to bounding stones while the metal pipe is prevented from oxidizing due to, e.g., mud or chemicals, thereby enhancing the corrosion resistance property of the heat conduction pipe.
Other heat conductive pipes, on the other hand, such as described in Japanese Patent Application Publication Nos. JA-9-42573, JA-9-136111, and JA-11-325778 have existed, wherein a long metallic flat plate is wound spirally on an outer circumference of the metal pipe to form a fin member in a projecting manner on the outer circumference of the metal pipe, thereby improving heat radiation property and endothermnic property of the heat conductive pipe.
The heat conductive pipe holding the resin coating layer as described in Japanese Patent Application Publication Nos. JA-8-188884 and JA-10-315295, however, has a problem in terms of the heat radiation property and the endothermic property thereof because the resin coating layer is thickly formed for improving shock resistance and the corrosion resistance, so it is difficult to improve heat exchange efficiency among fluids mutually flowing though the interior and exterior of the heat conduction pipe.
With the heat conduction pipe attaching the metal fin member in the projecting manner as described in Japanese Patent Application Publication Nos. JA-9-42573, JA-9-136111, and JA-11-325778, on the other hand, it is possible to obtain high heat exchange efficiency owing to the enlarged heat exchange area, but the anticorrosion plating layer on the surface of the metal pipe is easily damaged due to, e.g., the bounding stones, so there rises a problem with the corrosion residence.
Furthermore, the fin member made of the metallic material in a flat plate shape having a contact portion, is formed in a spiral shape and wound on the metal pipe, and therefore, spiral buckling is occurred due to resilient force of the metallic material as formed with wave form edges at the contact portion thereof in contact with the metal pipe, so that adhesion between the fin member of the contact portion and the outer circumferential surface cannot be done in a good manner, so that good thermal conductivity between the metal pipe and the fin member cannot be obtained.
To prevent the buckling phenomenon from occurring, both side end surfaces of the fin member in the spiral shape are secured to the metal pipe by clips, screws, or the like, but manufacturing process takes many steps, and further, the connection between the fin member and the metal pipe by the above-described process is not enough. A gap between the fin member and the metal pipe, therefore, needs to be plugged by, e.g., coating or brazing, so that the operation process is so complicated and that it is difficult to improve the productive efficiency.